High‐Temperature Treatment of Li‐Rich Cathode Materials with Ammonia: Improved Capacity and Mean Voltage Stability during Cycling

Erickson, Evan M.; Sclar, Hadar; Schipper, Florian; Liu, Jing; Tian, Ruiyuan; Ghanty, Chandan; Burstein, L.; Leifer, Nicole; Grinblat, Judith; Talianker, M.; Shin, Jungyeop; Lampert, Jordan; Markovsky, Boris; Frenkel, Anatoly I.; Aurbach, Doron

doi:10.1002/aenm.201700708

Cited by 157 publications

(133 citation statements)

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“…Electrodes were fabricated as described elsewhere . Briefly, 80 % active material was mixed with 10 % carbon black super‐P and 10 % Solef 5130 polyvinylidendifluoride (PVDF) binder in N‐methylpyrrolidone (NMP), and cast onto an Al foil (Strem) current collector at a loading of ∼4 mg/cm 2 .…”

Section: Resultsmentioning

confidence: 99%

“…These surface treatments may act as a non‐reactive barrier between the electrolyte solution and the cathode material, as well as a capping layer to prevent further oxygen release during cycling to limit spinel growth from the surface material . Chemical modification that induces surface passivation has been shown to help, as with ammonia gas (NH 3 ) or hydrazine (N 2 H 4 ) treatment . Since spinel formation at the surface is a necessity for activation of Li‐rich material, chemically pre‐forming a passivation layer prior to in‐situ electrochemical activation can help by ensuring the uniformity of this layer and minimizing its thickness .…”

Section: Introductionmentioning

confidence: 99%

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Fluorination of Li‐Rich Lithium‐Ion‐Battery Cathode Materials by Fluorine Gas: Chemistry, Characterization, and Electrochemical Performance in Half Cells

et al. 2019

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Mild fluorination of high‐energy nickel‐cobalt‐manganese (HE‐NCM) materials with low pressures of elementary fluorine gas (F2) at room temperature was systematically studied. The fluorinated HE‐NCM samples were analysed by ion chromatography, inductively coupled plasma mass spectrometry, FT‐IR spectroscopy, powder X‐ray diffraction, magic angle spinning NMR spectroscopy, scanning electron microscopy, thermo‐gravimetric analysis, differential thermal analysis, electrochemical testing, and X‐ray photoelectron spectroscopy. The treatment of the cathode materials with low pressures (a few hundred mbar) of elementary fluorine gas at room temperature led to the elimination of the basic surface film (LiOH, Li2CO3, Li2O, etc.), and the resulting thin amorphous LiF film led to increased capacity and long‐term stability of the battery. Impedance built‐up was greatly reduced for these systems throughout cycling. Fluorination with F2 only causes the formation of O−Me−F bonds (Me=Transition Metal), when treated with F2 at higher pressures. If O−Me−F bonds are formed, it may be detrimental to the electrode surface film resistance and cycle stability of the electrodes. However, it may be that the LiF surface content, which can expand as long as the LiMeO2 structure can be oxidized and Li+ can be extracted, has become too large and thus detrimental. Considering the evolution of differential capacity plots and taking into account the thermodynamic driving force of the F2 treatment, it is likely that the same activation processes that occur electrochemically in Li‐rich materials also occur chemically, when the material is exposed to F2. Differential capacity plots show enhanced Mn4+ reduction peaks upon lithiation, when the material was exposed to F2, only possible after activation of the Li2MnO3 phase. For this reason, we believe fluorination promotes to some extent an activation of this phase.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Fluorination of Li‐Rich Lithium‐Ion‐Battery Cathode Materials by Fluorine Gas: Chemistry, Characterization, and Electrochemical Performance in Half Cells

et al. 2019

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“…. The peak 5 of CT‐LRM owns higher voltage position and stronger intensity than that of NM‐LRM, which indicates the cathode material possesses faster kinetics to insert into Li layer after coating treatment …”

Section: Results and Discussmentioning

confidence: 94%

A Collaboration of Surface Protection and Bulk Doping for High‐performance Li‐rich Cathode Materials

Wang

Sun

et al. 2019

ChemistrySelect

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Li‐rich layered oxides (LLRO) are promising high energy‐density cathode, but always suffer from the oxygen loss in initial activation and gradual structure transformation during cycling, which leads to capacity degradation and potential decay. Here, we employ a simple strategy to achieve the collaboration of surface protection and bulk doping for improving the performance of Li‐rich material. Scanning electron microscope and transmission electron microscopy tests demonstrate that a nanoscale protective layer of magnesium pyrophosphate is uniformly coated on the Li‐rich material surface. X‐ray diffraction test indicates Mg2+ and P2O74− are incorporated into the crystal structure, which induces the larger lattice spacing and lower cation mixing. As a result, the resultant LLRO displays extremely high Coulombic efficiency of 91.8% and discharge capacity of 288.4 mAh g−1, showing prominent cycling stability of 89.2% after 200 cycles. Furthermore, our strategy also suppresses the attenuation of average voltage during cycling and the potential drop is only 0.56 mV per cycle from 25 th to 200 th cycle. The excellent electrochemical performance can be ascribed to the combined merits of surface protection and bulk doping. This strategy may provide some new insights into the design and synthesis of high‐performance electrode materials.

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“…In addition, surface modification with dopants such as F, Cl and other elements has also been identified as a promising performance-enhancing technique, frequently increasing structural stability and electrical conductivity by hindering electrolyte degradation and reducing impedance [14,15]. Specifically, surface N-doping by treatment with ammonia has been shown to effectively improve the electrochemical performance of spinel and Li-rich oxide layer materials, which is attributed to the formation of surface and oxygen defects and the nitridation of the active electrode material surface [16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Ammonolysed LiNi $$_{0.8}\hbox {Co}_{0.15}\hbox {Al}_{0.05}\hbox {O}_{2}$$ 0.8 Co 0.15

Yoon

2018

Bull Mater Sci

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In this work, ammonolysed LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA) prepared by co-precipitation and subsequent ammonolysis was investigated as a cathode material for Li-ion batteries with enhanced rate capability. Detailed structural and morphological property characterization demonstrated that ammonolysis results in the incorporation of a small amount of nitrogen into the surface layer of the afore-mentioned material. The electrochemical performances of NCA electrodes were measured by galvanostatic charging-discharging of the corresponding Li-ion cells, revealing that ammonolysed NCA exhibited higher capacity and rate capability than those of the pristine sample, i.e., after 20 cycles, the discharge capacity of the former equalled 176 mA h g −1 at a current density of 18.4 mA g −1 , remaining as high as 107 mA h g −1 at a high current density of 1840 mA g −1. This improved performance was ascribed to ammonolysis-induced surface changes, which reduced cell polarization during cycling and enhanced the electrochemical stability and reaction kinetics of NCA electrodes.

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High‐Temperature Treatment of Li‐Rich Cathode Materials with Ammonia: Improved Capacity and Mean Voltage Stability during Cycling

Cited by 157 publications

References 72 publications

Fluorination of Li‐Rich Lithium‐Ion‐Battery Cathode Materials by Fluorine Gas: Chemistry, Characterization, and Electrochemical Performance in Half Cells

Fluorination of Li‐Rich Lithium‐Ion‐Battery Cathode Materials by Fluorine Gas: Chemistry, Characterization, and Electrochemical Performance in Half Cells

A Collaboration of Surface Protection and Bulk Doping for High‐performance Li‐rich Cathode Materials

Ammonolysed LiNi $$_{0.8}\hbox {Co}_{0.15}\hbox {Al}_{0.05}\hbox {O}_{2}$$ 0.8 Co 0.15

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